Heritability of age at first calving in Canchim cows

Abstract

The age at first calving of 233 5/8 Charolais – 3/8 Zebu (sired by Charolais bulls) and 266 Canchim (5/8 Charolais – 3/8 Zebu) cows, raised in the State of São Paulo, were studied. Analyses of variance, including the fixed effects of year and month of birth of cow and sex of calf, and the random effects of sire of cow, were utilized to analyze the data. None of the effects included in the models affected significantly age at first calving. Least squares means for age at first calving were 1003.83 ± 12.43 days (33.00 ± 0.41 months) and 1022.54 ± 12.99 days (33.63 ± 0.43 months) for the 5/8 Charolais - 318 Zebu and Canchim cows, respectively. Heritability estimates, obtained by the paternal half-sister method, were in the same order, -0.066 ± 0042 and -0.032 ± 0.108, suggesting that, under the conditions of this study, genetic progress by selection would be practically zero.